One came back, another Net went out, a couple were in, then out or out, then in.

And the Nets’ defense remained a critical topic.

Jarvis Hayes, felled by a strained left hamstring over two weeks ago, went through practice yesterday. Good thing because Yi Jianlian sat out with a sore right foot. Keyon Dooling, who has been battling some bug, began practice, looked good, then had to call it a day and go back for an IV drip.

In other A.M.A. news, Eduardo Najera remained out with a sore left wrist and Stromile Swift stayed down with a lower-back bruise. So it couldn’t be any less rosy for the Nets who complete their exhibition schedule tonight at the Garden against Knicks, right?

Wrong. Devin Harris suffered a slightly strained right ankle. Both he and Yi are not considered serious – Yi claimed his foot was “just a little sore” and seemed unconcerned. But coach Lawrence Frank, calling Dooling and Hayes “game-time decisions,” said Yi would sit, especially with tomorrow being an off day. A couple days off should help.

Hayes seemed utterly grateful to not have to continue watching – the fate that befell Najera who “jumped in and Timmy [trainer Walsh] tried to tackle him. He’s thirsty like a Rottweiler,” Frank said.

“I feel good. I did a lot of conditioning while I was out. Obviously when you don’t play for a couple weeks, you get a little rusty, but I’ll get that back quick,” said Hayes. Nothing I’m worried about.”

Unlike the defense. The Nets in the past two games surrendered 232 points, given up 26-of-52 shooting on 3-pointers. That’s two games, OK? In their six games (2-4), they’ve yielded an average of 102.7 points. That’ll get them far – as far as the lottery.

“We have to be better at guarding the ball, we have to be better at our position defense,” Frank stressed. “There’s no substitute. Everyone plays hard. But we’ve got to understand that our formula is that we’ve got to try to outwork people.”

*

As expected, the Nets waived Eddie Gill, Julius Hodge, Brian Hamilton and Keith Van Horn to get the roster down to 15 . . . Nets and Knicks supporting Courts of Dreams Foundation fundraiser at Sports Club/LA, E. 61st St. tomorrow to raise money to repair basketball playground courts in city. There will be a clinic and raffles. Execs Kiki Vandeweghe and Donnie Walsh plus coach Mike D’Antoni and players for both teams expected. For info, go to info@pinnaclehoops.com.